350i Misfires under light Throttle - Fine under full!!
Discussion
I have just returned from the TVR club season opener meet. I did 165 miles to get there with no issue but no motorways. On the way home, I came down on the motorway and discovered a misfire.
The car starts and runs fine and accelerates Ok too. It is when you are cruising and just lightly press the throttle that it hesitates and misfires a little. If I put my foot down, the issue goes away.
I checked AI and it says with great confidence the following:
"The most likely cause on a TVR 350i (Rover V8 + flapper‑EFI) that misfires/hesitates on light throttle but pulls cleanly on heavy throttle is a weak or failing ignition component, especially the ignition amplifier (module) or coil.
That pattern — bad at light load, fine at heavy load — is a classic Rover V8 giveaway.
The ignition amplifier on the side of the distributor is the #1 suspect, followed closely by the coil and HT leads.
Light‑throttle misfire is almost never fuel on a flapper‑EFI Rover V8 — it’s almost always ignition breakdown.
Most likely causes (ranked)
Ignition amplifier (Lucas AB14 module)
Heat‑soaks and fails intermittently
Classic symptom: light‑throttle misfire, OK when floored
Often worse when warm
Cheap to replace or relocate to a heatsink"
Does that sound likely? I am supposed to be off to the Spa Classic in ten days so I need to get it properly sorted out. Any help would be greatly appreciated!
The car starts and runs fine and accelerates Ok too. It is when you are cruising and just lightly press the throttle that it hesitates and misfires a little. If I put my foot down, the issue goes away.
I checked AI and it says with great confidence the following:
"The most likely cause on a TVR 350i (Rover V8 + flapper‑EFI) that misfires/hesitates on light throttle but pulls cleanly on heavy throttle is a weak or failing ignition component, especially the ignition amplifier (module) or coil.
That pattern — bad at light load, fine at heavy load — is a classic Rover V8 giveaway.
The ignition amplifier on the side of the distributor is the #1 suspect, followed closely by the coil and HT leads.
Light‑throttle misfire is almost never fuel on a flapper‑EFI Rover V8 — it’s almost always ignition breakdown.
Most likely causes (ranked)
Ignition amplifier (Lucas AB14 module)
Heat‑soaks and fails intermittently
Classic symptom: light‑throttle misfire, OK when floored
Often worse when warm
Cheap to replace or relocate to a heatsink"
Does that sound likely? I am supposed to be off to the Spa Classic in ten days so I need to get it properly sorted out. Any help would be greatly appreciated!
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